Summary

Myocarditis describes a heterogeneous group of disorders characterized by myocardial inflammation in the absence of predominant acute or chronic ischemia.

Can affect all age groups with an apparent slightly higher incidence in males than females and equal incidence in black people and white people.

May present as fulminant, acute, or chronic myocarditis.

Treatment is usually supportive care and conventional heart failure therapy. More severe presentations may need aggressive vasopressor or inotropic pharmacologic support or mechanical hemodynamic assist devices such as intra-aortic balloon pump or left ventricular assist device. Occasionally certain cases do not respond to conventional therapy and progress to heart transplantation or death.

Prognosis is variable but is related to presentation and underlying etiology. Most cases of viral myocarditis are asymptomatic and spontaneously resolve. Patients who present with mild to moderate heart failure tend to improve or recover but may progress to chronic severe heart failure. Surprisingly, patients who present with fulminant, acutely decompensated heart failure almost universally recover back to baseline function, if death is prevented through management in the acute phase.

Definition

Myocarditis is clinically and pathologically defined as inflammation of the myocardium in the absence of the predominant acute or chronic ischemia characteristic of coronary artery disease. It is a clinical syndrome of nonischemic myocardial inflammation resulting from a heterogeneous group of infectious, immune, and nonimmune diseases. Histopathologically, it is characterized by an inflammatory cellular infiltrate with or without evidence of myocyte injury.
[1]Aretz HT, Billingham ME, Edwards WD, et al. Myocarditis. A histopathologic definition and classification. Am J Cardiovasc Pathol. 1987 Jan;1(1):3-14.
http://www.ncbi.nlm.nih.gov/pubmed/3455232?tool=bestpractice.com
[Figure caption and citation for the preceding image starts]:
Histologic findings in a patient with giant cell myocarditis. A: severe myocardial necrosis and fibrotic replacement of the cardiomyocytes with granulation tissue and fibrosis is present in a section from the anterolateral left ventricular wall; B: a sharp demarcating border between vital and necrotic myocardium is seen, confirmed by additional immunohistochemical staining for myoglobin; C: at the inflammatory border, cells consisting of prominent multinucleated giant cells, macrophages, lymphocytes, and eosinophilic granulocytes are seen in close proximity to vital myocardium; D: immunohistochemical staining for complement 4d is positive in all vessels, suggestive of complement cascade activation
From: Rasmussen TB, Dalager S, Andersen NH, et al. BMJ Case Reports 2009; doi:10.1136/bcr.09.2008.0997 [Citation ends].